I did a self diagnostic test on my ECU today and i'm getting back two error codes, the temperature sensor and vechicle speed sensor. I understand why i have the error for the temp sensor because my fans don't kick on at all. But what is stumping me is the vechicle speed sensor. Any help on either of these. by the way my temp sensor i already changed and the fans still don't kick on.

Did you replace the correct temp sensor?
(There are two, one for the ECU, one for the temp gauge).

Can't help you on the speed sensor.

I replaced the one for the ecu already but maybe i should change the other 2. I'm gonna change the thermostat anjd coolant first to see if that could be the culprit i heard our engines are real sensitive to air in the coolant system

What year? I can lookup in my 91' FSM what's between the temp sensor and your radiator fan (electrically). I'm sure there is a relay in there somewhere that is ECU controlled, probably a fuse/fusible link too.

I can also lookup what to check for your speed sensor, but again it will be based on the 91' FSM.

i have a 93 nx2000 but i alreay have a fsm. Thanks though